Godot 4 with GDExtension help needed

Hi I'm learning Godot 4 (beta 10) with GDExtension and I need help learning the new multiplayer nodes. I am trying to make a simple project where I move a sprite between two windows (server and client) but with some basic code, I'm segmentation fault. I need a Godot expert who has knowledge with GDExtension to help me with this issue. More work will be available once I need further help with other aspects of Godot GDExtension. Thanks